Viral infection causes various disorders, including cancer. For example, human papillomaviruses (HPVs) infection accounts for the development of several cancers, in particular the cervical cancer, the second leading cause of cancer death in women worldwide (Schwarz, Expert Rev Vaccines 7:1465-73, 2008). It was estimated that about 493,000 new cervical cancer cases were diagnosed per year (Parkin et al., CA Cancer J Clin 55:74-108, 2005). Vaccines are being developed for preventing infections with cancer-causing viruses, treating existing cancer, or preventing the development of cancer in high risk individuals. However, many are not effective. There is a need for effective vaccines and related reagents.